Control mechanism and system and method for steering distal extremity of a flexible elongate member

ABSTRACT

A device compressing a flexible elongate member having proximal and distal extremities and having a plurality of circumferentially spaced-apart elements having a characteristic disposed in the distal extremity. A control mechanism is secured to the proximal extremity of the flexible elongate member. The control mechanism has a housing adapted to be grasped by a human hand. A first control member is slidably mounted in the housing. A second control member is rotatably mounted in the housing. The first and second control members are accessible to the fingers of the human hand grasping the housing. Electrical circuitry couples the first and second control members to the elements whereby when the first and second control members are moved, the distal extremity of the flexible elongate member is moved in accordance with the positioning of the first and second control members.

This is a division of application Ser. No. 07/983,963 filed Dec. 1,1992, now U.S. Pat. No. 5,330,466.

This invention relates a control mechanism and system and method forsteering the distal extremity of a flexible elongate member, as forexample a catheter.

In U.S. Pat. No. 5,238,005, there is disclosed a joystick-type ofcontrol for controlling the distal extremity of a flexible elongatemember. In certain applications, as for example in endocardial ablation,use of such a joystick control has been found to be undesirable becausein such a joystick control it is necessary to hold the joystick in thedesired position because as soon as it is released it normally returnsto its home position typically under the force of springs. In anablation procedure which may take a period of time, it is difficult tohold the joystick in the desired location for that period of time. Also,in conjunction with a joystick control, it has been found that it isdifficult to make certain movements. For example, if it is desired tohelp the same bend in the distal extremity of the catheter but to moveit a few degrees to the right or the left, this is difficult to dowithout changing the amount of bend in the distal extremity of thecatheter. There is, therefore a need for a new and improved controlmechanism, system and method for steering the distal extremity of aflexible elongate member.

In general, it is an object of the present invention to provide acontrol mechanism and system and method for steering the distalextremity of a flexible elongate member which facilitates retaining thedistal extremity of the flexible elongate member in a predeterminedposition.

Another object of the invention is to provide a control mechanism,system and method of the above character which permits a small amount ofmovement of the distal extremity of the catheter in one directionwithout affecting the position of the distal extremity of the flexibleelongate member in another direction.

Another object of the invention is to provide a control mechanism,system and method of the above character in which the desired motion forthe distal extremity of the flexible elongate member is determined byfirst and second controls.

Another object of the invention is to provide a control mechanism,system and method of the above character in which the first controlrepresents the amount of bend placed in the distal extremity and whereinthe second control determines the angle of the bend.

Another object of the invention is to provide a control mechanism,system and method of the above character in which the first and secondcontrols can be actuated independently of each other.

Another object of the invention is to provide a control mechanism,system and method of the above character which is user friendly.

Another object of the invention is to provide a control mechanism,system and method of the above character which can be held by a humanhand in which the first and second controls can be operated by use ofthe fingers of the same hand holding the control mechanism.

Additional features and objects of the invention will appear from thefollowing description in which the preferred embodiments are set forthin detail in conjunction with the accompanying drawings.

FIG. 1 is an isometric view showing a control mechanism and systemincorporating the present invention.

FIG. 2 is a cross-sectional view taken along the line 2--2 of FIG. 1.

FIG. 3 is an enlarged detail view partially in cross section of thecontrol mechanism shown in FIG. 1 with the top plate removed.

FIG. 4 is a cross-sectional view of the control mechanism shown in FIG.1.

FIG. 5 is a top plan view of an alternative embodiment of a controlmechanism showing coarse and fine controls.

FIG. 6 is a circuit diagram of the electronics in digital form utilizedin the control system.

FIG. 6a is a portion of a circuit diagram similar to that shown in FIG.6 but making provision for both coarse and fine controls.

FIG. 7 is a circuit diagram of the electronics in analog form utilizedin the control system.

In general the control system of the present invention consists of aflexible elongate member having proximal and distal extremities andhaving a plurality of circumferentially spaced-apart elements having anegative coefficient of expansion disposed in the distal extremity. Acontrol mechanism is secured to the proximal extremity of the flexibleelongate member. The control mechanism is provided with a housing whichis adapted to be grasped by a human hand. A first control member isslidably mounted in the housing and a second control member is rotatablymounted in the housing. The first and second control members areaccessible to the fingers of the human hand grasping the housing.Electrical means is provided for coupling the first and second controlmembers to the elements having a negative coefficient of expansionwhereby when the first and second control members are moved, the distalextremity of the flexible elongate member is moved in accordance withthe positioning of the first and second control members.

More in particular, as shown in the drawings, the control mechanism andsystem for steering the distal extremity of a flexible elongate memberincludes a control system 11 and a control mechanism 12. A flexibleelongate member 16 is provided which has proximal and distal extremities17 and 18. The flexible elongate member 16 is formed of a suitablematerial such as plastic and is provided with a plurality of lumens. Asshown in FIG. 2, four of such lumens 21, 22, 23 and 24 have beenprovided which are spaced apart circumferentially as well as a centrallydisposed lumen 26. Flexible elongate elements 31, 32, 33 and 34 aredisposed in the lumens 21-24 and have a characteristic which isactivated by heat. As disclosed in U.S. Pat. No. 5,238,005, suchelements can have a negative coefficient of expansion or alternativelycan have a shape-memory. The distal extremities of these elements 31-34are connected to a common return conductor 36 provided in the lumen 26.The return conductor 36 extends to the proximal extremity 17 of theflexible elongate member 16. Similarly, conductors (not shown) areprovided within the flexible elongate member element 16 which areconnected to the elements 31-34 having a negative coefficient ofexpansion and extend through the flexible elongate member to theproximal extremity 17.

The control mechanism 12 is mounted on the proximal extremity 17 of theflexible elongate tubular member 16. It consists of an elongatecylindrical housing 41 which is sized so that it is adapted to fitwithin the human hand, for example it can have a diameter such asapproximately 1" and a length of approximately 6". The housing can beformed of a suitable material such as aluminum or plastic and isprovided with fluting 42 extending longitudinally of the housing. Thefluting 42 facilitates grasping of the housing so that it will not slipwithin the hand. The housing 12 is provided with an elongate recess 43which extends longitudinally of the housing and which opens through aflat surface 44 provided on one side of the housing 41. A flat or planarcover plate 46 is mounted on the surface 44 and covers the recess 43 andis secured to the surface 44 by suitable means such as screws 47.

A device representing linear motion such as a linear potentiometer 51 ismounted in the recess and is secured to the cover plate 46 by suitablemeans such as a pair of screws 52. The linear potentiometer 51 includesa slider 53 which is adapted to move longitudinally of the potentiometerand which extends through an elongate slot 54 provided in the top coverplate 46 and extending longitudinally of the cylindrical housing 41. Afirst control member 56 is provided for the housing 41 and is mounted onthe slider 53. The control member 56 is provided with opposed arcuatesurfaces 57 which are adapted to be engaged by two fingers of the hand.

A device representing rotary motion such as a rotary potentiometer 61 isalso provided within the recess 43 of the housing 41 and is mounted on aplate 62 extending transversely in the recess 43 of the housingunderlying the top cover plate 46. The rotary potentiometer 61 isprovided with a control shaft 63 which extends through the plate andwhich has mounted thereon a second control member 64 in the form of arotary knob which extends upwardly through a rectangular slot 66provided in the cover plate 46. The knob 64 is provided with fluting 67to facilitate frictional engagement between the knob and the finger ofthe human hand engaging the knob.

The proximal extremity 17 of the flexible elongate member 16 is securedto the housing 41 by a fitting 71 through which the conductorshereinbefore described extend and are connected to a cable 72 thatextends through the recess 43 underlying the rotary potentiometer 61 andthe linear potentiometer 51 and through a fitting 73 mounted on theother end of the housing 41. The fitting 73 is connected to a flexiblecable 74 which is connected to a connector 76. The connector 76 isremovably connected to another connector 77 provided on control console78. Additional cables 81 and 82 are provided within the housing and areconnected to the connector 73 and extend through the cable 74 to thecontrol console 78. A light-emitting diode 86 is provided underlying ahole 87 in the top cover plate 46 to indicate when the power is on.

Another embodiment of a control mechanism similar as that shown in FIGS.1, 2, 3 and 4 is shown in FIG. 5 which differs only in that anadditional control member 91 has been provided. The control member 91 isin the form of a circular knob as is the control member 64 and extendsthrough another rectangular slot 92 forward of the slot 54 in the coverplate 46. The additional control member 64 is connected to anotherrotary potentiometer (not shown) in the same manner as the controlmember or knob 64 is connected so that the control member 64 can providea coarse adjustment and the control member 91 can provide a fineadjustment for controlling the distal extremity of the flexible elongatetubular member 16.

Operation and use of the control mechanism and system in performing themethod of the present invention may now be briefly described inconjunction with the digital circuitry which is shown in FIG. 6. Asshown in FIG. 6, the digital circuit includes the linear potentiometer51 which is provided with the wiper 53 engaging or contacting the linearresistance 101 which is connected between ground and a 5-volt supply andcan be divided into five separate resistances 101-106 of a suitablevalue, as for example 10 kilo-ohms to provide a resistor having a totalvalue of 50 kilo-ohms so that there is a 1-volt drop across eachresistor starting from ground. The rotary potentiometer 61 which isprovided with the wiper 63 engages a resistance of a suitable value, asfor example 125 kilo-ohms, which is connected between a 5-volt supplyand ground. The potentiometer 61 is divided into five separate resistors111-116 of 25 kilo-ohms each so that there is a 1-volt drop between eachresistor. In rotation of the second control member 64 through 360° ofrotation and more, the voltage would be 0 at 0°, 1 volt at 90°, 2 voltsat 180°, 3 volts at 270° and 4 volts at 360°, with the voltage againdropping to 0 shortly thereafter at the 0° point to again repeat theprogression of voltages. Thus it can be seen that the rotarypotentiometer 61 can be moved through 360° and the rotation continued.

Movement of the first control member to position the slider 53 to adjustthe bend in the distal extremity of the flexible elongate member 16produces a voltage which is supplied through a buffer amplifier 121 to asecond channel of a six-channel A-to-D converter 122. The output voltageon the wiper 63 of the rotary potentiometer is supplied through thebuffer amplifier 126 directly to the first channel of the A-to-Dconverter 122. The A-to-D converter is connected by a bus 127 to amicroprocessor 128 which is controlled by a crystal 129. As shown, themicroprocessor 128 is connected to a positive voltage and to ground. Itis in communication with a ROM 131 through a bus 132. The ROM is alsoconnected to a positive voltage and ground, as shown.

The microprocessor 128 is also provided with four inputs identified asQ1, Q2, Q3 and Q4 which represent the first, second, third and fourthquadrants for rotational movement of the distal extremity of theflexible elongate member 16. In order for the microprocessor to do itscalculations, it must know from an angular standpoint which quadrant thedistal extremity 18 of the flexible elongate member 16 is in and inwhich direction it is moving. Thus, by way of example let it be assumedthat the rotary potentiometer is moved through an angle of 45° from 0°to produce 0.5 volt on the wiper 63. This 0.5 volt of information issupplied through the buffer amplifier 126 to three comparators 136, 137and 138 which are provided with references 141, 142 and 143,respectively. By way of example, the references for the comparator 136can be 1 volt, for comparator 137, 2 volts, and for comparator 138, 3volts. Thus, when the output from all three comparators 136, 137 and 138is low this indicates that the wiper 63 is at an angle of less than 90°and a signal would be supplied through the digital inverter 146 to theQ1 input to the microprocessor 128.

Let it be assumed by way of example that the second control member 64has been moved to a 135° angle to produce a voltage of 1.5 volts whichwould mean that the comparator 136 would go high and this output issupplied to AND gate 147 which supplies a voltage to the Q2 input of themicroprocessor 128. Similarly, when the second control member 64 ismoved into the next quadrant, the output from the comparators 136 and137 are both high and a voltage is supplied to the AND gate 148 to causea signal to be supplied to the Q3 input to the microprocessor 128. Whenthe angle of the second control member 64 is greater than 270° theoutput from the comparators 136, 137 and 138 will all be high and asignal will be supplied to the Q4 input of the microprocessor 128. Eachof the AND gates 147 and 148 has one inverting input. The first AND gate147 takes its inputs from the first and second comparators 136 and 137,and the second AND gate takes its inputs from the second and thirdcomparators 137 and 138. Thus, it can be seen that the four signalssupplied on the inputs Q1 through Q4 inform the microprocessor 128 whichquadrant the distal extremity or tip of the flexible elongate member 16is in. The ROM 131 contains a program for the microprocessor and causesthe microprocessor to utilize angle information supplied to themicroprocessor to calculate the sine and cosine of the angle to multiplyit with the amplitude information which has been supplied to it from thelinear potentiometer 51.

The information generated by the microprocessor is supplied through abus 151 to a four channel D/A converter 152 which is connected to fouroperational amplifiers 156, 157, 158 and 159. These amplifiers drivecommon emitter transistors 161-164 which serve as constant currentsources. These constant current sources are connected directly to theflexible elongate elements 31, 32, 33 and 34 having a negativecoefficient of expansion for controlling the distal extremity 18 of theflexible elongate member 16. Thus, it can be seen that the currentswhich are generated can be utilized for controlling the movement of thedistal extremity of the flexible elongate member. In order for themicroprocessor 128 to know precisely what currents are to be supplied tothe elements 31, 32, 33 and 34, means is provided for sensing thevoltages developed across the elements 31-34 and consists of four lineswhich are connected to the elements 31, 32, 33 and 34 and which areconnected to the inputs of buffer amplifiers 166, 167, 168 and 169, theoutputs of which are connected into the four remaining channels of theA-to-D converter 122. This makes it possible to monitor the resistancechanges in the four elements 31, 32, 33 and 34. The resistance changesin the elements 31, 32, 33 and 34 can be readily measured because of theresistance changes as the elements 31-34 become heated.

When it is desired to provide a fine control for the rotary motion ofthe digital extremity of the flexible elongate member 16, the circuitrywhich is shown in FIG. 6A can be provided, in which the coarse controlknob 64 covers a coarse range from 0.5 to 3.5 volts and the fine control91 covers a range from ±0.5 volts so that the total voltage can bevaried from 0-4 volts to provide the four quadrants hereinbeforedescribed. The output from the amplifier 126 is supplied through aresistor 171 to one of the inputs of the summing amplifier which hasadded to it a voltage supplied through a resistor 173 connected to awiper 174 controlled by the knob 91 of a rotary potentiometer 176connected between a +5 volts and a -5 volts and divided into fiveincrements of resistance. Thus, a coarse control knob 64 can be utilizedfor providing a coarse movement of the distal flexible elongate memberto the desired approximate position, after which the fine control knob91 can be utilized to move the tip or distal extremity 18 in a smallerincrement to the desired position.

An analog circuit for performing the same functions as performed by thedigital circuit shown in FIG. 6 is shown in FIG. 7. The linearpotentiometer 51 and the angular potentiometer 63 are connected in asimilar manner as in FIG. 6. The output from the angular potentiometer61 is supplied to a buffer amplifier 201 and, similarly, the output fromthe linear potentiometer 51 is supplied to a buffer amplifier 202. Theoutput from the buffer amplifier 201 is supplied to three comparators206, 207 and 208 which, by the logic hereinbefore described inconjunction with FIG. 6, provides four output signals on linesidentified as Q1, Q2, Q3 and Q4 to provide the necessary quadrantinformation which is used to determine which of the four steeringelements will be energized. Thus, if the distal extremity 18 of theflexible elongate member 16 is in the first quadrant, only two leadscorresponding to Q1 and Q2 will be actuated. If it is in the secondquadrant, the leads Q2 and Q3 will be actuated. If it is in the thirdquadrant, leads Q3 and Q4 will be actuated, and if it is in the fourthquadrant, leads Q4 and Q1 will be actuated. The comparators 206, 207 and208 are provided with three references 211, 212 and 213 of 1, 2 and 3volts, respectively, by the voltage divider network 209. The outputsfrom the comparators 206, 207 and 208 are supplied to AND gates 211 and212 and three inverters 216,217 and 218. The quadrant outputs Q throughQ4 are connected to the control input of analog switches 221, 222, 223and 224. The output of the analog switches 221, 222, 223 and 224 areinterconnected as shown and provide an input to the buffer amplifier226. The combined outputs of the analog switches take on a value of 0 V,1 V, 2 V or 3 V depending on the quadrant that the angular potentiometer61 is in. The output of the buffer amplifier 226 is added to the outputof an inverting amplifier 227 and is supplied to the input of the addingamplifier 228 which has its output supplied to an inverting amplifier229 which provides a scaled value of the angle to the sine and cosinefunctions are represented by the circuitry shown in the conventionalcircuitry in blocks 241 and 242.

The outputs of the sine and cosine function blocks 241 and 242 aresupplied to multipliers 261 and 262 which serve to multiply the angleinformation supplied by the sine and cosine blocks with the amplitudeinformation supplied from the buffer amplifier 202 connected to thelinear potentiometer 51. Thus, the output of the amplifier 261 would besine θ multiplied by the amplitude. Similarly, the same amplitude ismultiplied by the multiplier 262 with cosine θ. The output from themultiplier 262 is supplied to the inputs of analog switches 266, 267,268and 269 which have their outputs connected to the inputs of operationalpower amplifiers 271, 272, 273 and 274. The outputs of these operationalamplifiers are connected to the flexible elongate elements 31, 32, 33and 34 having negative coefficients of expansion. Similarly, the outputof the multiplier 261 is connected to the inputs of analog switches 276,277, 278 and 279 and which also have their outputs connected to theoperational amplifiers 271, 272, 273 and 274. The control inputs of theanalog switches 266-269 and 276-279 are under the control of the Q1, Q2,Q3 and Q4 leads. Thus, it can be seen that means has been provided forsupplying predetermined amounts of energy to the flexible elongateelements 31-34, and thereby controlling the distal extremity of thecatheter. The amount of energy supplied to one of these elements isproportional to the value of the A sine θ or A cosine θ when A is theamplitude encoded by the linear potentiometer 51 and θ is the angleencoded by the rotary potentiometer 61. Thus, by way of example, theelement 31 could be supplied with current proportional to A cosine θ andthe element 32 could be supplied with current proportional to A sine θ.As the angle increases, A cosine θ becomes smaller and A sine θ becomeslarger At 90°, for example, A cosine θ is 0 and all of the energy issupplied to the one element 32. Thus it can be seen with the presentcircuitry, as the rotary potentiometer is moved, the amount of currentto be supplied to the elements is calculated on the fly.

It is apparent that from the foregoing that there has been provided acontrol mechanism system and method for the steering of the distalextremity of a flexible elongate member by which the desired movement ofthe distal extremity can be accomplished by movement of a slide memberand a rotary member representing, respectively, the bending and rotarymotion of the distal extremity of the flexible elongate member. Thecontrol mechanism and system is user friendly and can be easilyoperated.

It should also be pointed out that instead of using potentiometers otherencoding devices such as capacitive or optical encoders or simplymovable wiper contacts engaging stationary contacts can be used. Alsothe potentiometers can be replaced with three position rocker switchesor pushbutton switches, which would allow a counter to count for bendingand right or left for rotation. The output of the counter would bedirectly connected to a microprocessor, or an analog voltage could beprovided by connecting the counter to a DA converter.

What is claimed is:
 1. A control mechanism adapted to fit in a humanhand having fingers and for use with a flexible elongate member havingproximal and distal extremities comprising a housing adapted to besecured to the proximal extremity of the flexible elongate member, saidhousing being formed so that it fits within the human hand, a firstdevice adapted to control linear motion mounted in the housing andhaving a first movable control member and a second device adapted tocontrol rotary motion mounted in the housing and having a second controlmember, said first and second control members being adapted to beengaged by the fingers of the hand holding the housing, and a thirddevice adapted to control rotary motion mounted in the housing andhaving a third movable control member adapted to be engaged by a fingerof a hand holding the housing, one of the second and third devicesadapted to control rotary motion including means for providing a coarsecontrol and the other of the second and third devices for controllingrotary motion including means for providing a fine control.
 2. Amechanism as in claim 1 wherein said first device includes meanspermitting said first control member to be movable longitudinally of thehousing and said second device includes means permitting said secondcontrol member to be rotatable with respect to the housing.
 3. A controlmechanism for use with a flexible elongate member having proximal anddistal extremities to be used in negotiating a vessel in the human bodycomprising a housing adapted to be secured to the proximal extremity ofthe flexible elongate member, said housing being formed so that it fitswithin a human hand, first and second electrical output devices mountedin spaced apart positions on the housing, said first and secondelectrical output devices each having a control member mounted in thehousing adapted to be engaged by a finger of the human hand holding thehousing, said first and second electrical output devices including meansfor supplying first and second electrical signals for use in theflexible elongate member, the control member for the first electricaloutput device being mounted in the housing for movement longitudinallyof the housing and the control member for the second electrical outputdevice being mounted in the housing for rotational movement with respectto the housing.